In the fabrication of non-planar transistors, silicon germanium alloys, especially germanium, may be deposited in trenches between shallow isolation features typically fabricated from a dielectric film such as undoped silicon oxide. The inventors have observed that, germanium films erode more readily than silicon films when employing conventional chemical mechanical planarization (CMP) techniques. As a result, film removal and uniformity control can be more difficult when using CMP techniques for germanium films than for silicon films. The same behavior may occur for films of germanium tin alloys and certain III-V alloys.
Accordingly, the present invention provides improved methods for chemical mechanical planarization of patterned wafers.